Three to five days after giving birth, your milk supply increases.
That can cause engorgement, so can a missed feeding.
Watch a video on how to express breast milk. Apart from discomfort, the main concern is that - with nipples often flattened against a swollen, sore and warm breast, your baby may have difficulty latching on.
Resources & Links:
VIDEO: Admission to Postpartum - Keeping Your Baby Skin-to-Skin
VIDEO: Baby's Feeding Cues and Behaviours
VIDEO: Breastfeeding Positions
VIDEO: Hand Expressing Milk
VIDEO: Latching Your Baby